Digital Television Transmission Standards

kcarnold wrote to us with a discussion piece about the digital television standards, covering both what the government is trying, the Sinclair effort as well as some of the technical aspects. Click below to read more or just add your voice to the debate.

I wanted to know what Slashdotters thought about the COFDM vs. 8VSB digital television transmission standard issue. However, I was suprised to find nothing related to this topic in a Slashdot search. This is an important issue, and it's a big one: almost half of the broadcast television stations in the US support the movement, lead by Sinclair Broadcast Group, to change the standard.

Here's the issue (another NY Times article talks about this -- search for DTV). Digital television, or DTV, is projected to replace America's current NTSC transmission system sometime in the earle 21st century. Stations have already begun to move to the new trasmission format. It promises better picture quality, no ghosting, and (here's the big one for "nerds") 19.2 megabits per second of raw binary data. One of the major forseen applications is delivering data like the data on the PointCast Network to mobile devices. Of course, however, the main application is television. Broadcasters have a choice: either they can transmit one channel of amazingly high-resolution, stunningly detailed high-quality video (HDTV), or several channels (4, I think) of standard-quality video, which is better than the video of the current system because there is no ghosting and fading up until a point where it doesn't come in at all. The issue centers over that point.

The current system is known as 8VSB, and it passed advanced laboratory testing and even some basic field testing almost ten years ago. However, last year, when Sinclair did actual, in-home, average-viewer's-setup testing of this system, it didn't work as well as the NTSC system. They could not receive HDTV signals from a station near an NTSC station whose picture came in clear. Then Sinclair did more, and more detailed, tests at home in Baltimore. This time they brought for comparison a sample modulator for the European transmission system called COFDM, and a demodulator / decoder box to receive it. They tried it in streets with tall buildings, parking garages, and apartments, all places where multipath, which causes ghosting, is prevalent. Each time they tested the two systems--European COFDM and American 8VSB, the COFDM receiver picked out its signal without fail--"It was hard to find a place where it didn't work," says my dad, who was part of the testing--but it was hard to find a spot where 8VSB would work. Continued testing convinced Sinclair officials that the current system would not be able to work in the real world, and are pushing for a change to COFDM, a system that has been proven in Europe. They wrote up a petition to the FCC, and almost half of the television stations of the US have signed it.